Manufacture of solid phosphoric acid catalysts



United States PatentO MANUFACTURE OF SOLID PHOSPHORIC ACID CATALYSTS NoDrawing. Application September 24, 1952, Serial No. 311,318

13 Claims. (Cl. 252-435) This application is a continuation-in-part ofmy copending application Serial No. 99,121, filed June 14, 1949, nowabandoned.

This invention relates to the manufacture of solid catalysts useful inaccelerating various reactions of unsaturated organic compounds. In amore specific sense, the invention is concerned with the production of aparticular type of solid catalyst which is highly active in acceleratingand directing olefin conversion reactions, particularly olefinpolymerization reactions. This catalyst has also relatively lowcorrosive properties when employed in the ordinary commercial apparatuscomprising various types of steel.

One object of this invention is a method of producing a highly activehydrocarbon conversion catalyst.

Another object of this invention is a highly active catalyst suitablefor use in the polymerization of olefinic hydrocarbons and in otherconversion reactions involving olefins.

One specific embodiment of this invention relates to a process formanufacturing a solid catalyst which comprises mixing a phosphoric acidand an alkyl orthosilicate to form a composite, and calcining saidcomposite.

An additional embodiment of this invention relates to a process formanufacturing a solid catalyst which comprises mixing a polyphosphoricacid and an alkyl orthosilicate to form a composite, and calcining saidcomposite.

Another embodiment of this invention relates to a process formanufacturing a solid catalyst which comprises mixing a polyphosphoricacid and ethyl orthosilicate to form a composite, and calcining saidcomposite.

A further embodiment of this invention relates to a process formanufacturing a solid-catalyst which comprises mixing pyrophosphoricacid and an alkyl orthosilicate to form a composite, and calcining saidcomposite.

A still further embodiment of this invention relates to a process formanufacturing a solid catalyst which comprises mixing pyrophosphoricacid and ethyl orthosilicate to form a composite, and calcining saidcomposite.

The essential and active ingredient of the solid catalysts which aremanufactured by this process for use in organic reactions is an acid ofphosphorus, preferably one in which the phosphorus has a valence of 5.The acid may constitute 16% to about 75% or more of the catalyst mixtureultimately produced, and in most cases, i over 50% by Weight thereof. Ofthe various acids of phosphorus, orthophosphoric acid (HsPOr) andpyrophosphoric acid (H4P2O7) find general application in the primarymixtures, due mainly to their cheapness and to the readiness with whichthey may be procured although the invention is not restricted to theiruse but may employ any of the other acids of phosphorus insofar as theyare adaptable. However, it is not intended to infer that the differentacids of phosphorus, which may be employed, will produce catalysts whichhave identical effects upon any given organic reactions as each of thecatalysts pro- "ice duced from different acids and by slightly variedprocedure will exert its own characteristic action.

In using orthophosphoric acid as a primary ingredient, differentconcentrations of the aqueous solution may be employed fromapproximately to or acid containing some free phosphorus pentoxide mayeven be used. By this is meant that the ortho acid may contain adefinite percentage of the pyro acid corresponding to the primary phaseof dehydration of the orthophosphoric acid. Within these concentrationranges, the acids will be liquids of varying viscosities, and readilymixed with the aforementioned alkyl orthosilicate.

In practice it has been found that pyrophosphoric acid corresponding tothe formula H4P2O7 can be incorporated with alkyl orthosilicates attemperatures somewhat above the melting point of the phosphoric acid andthe period of heating which is given to the pyro acid-siliceous materialor to the mixtures of other polyphosphoric acids and alkylorthosilicates may be different from that used when the ortho acid is soemployed.

Triphosphoric acid which may be represented by the formula HsPsOro mayalso be used as a starting material for preparation of the catalysts ofthis invention. These catalytic compositions may also be prepared fromthe siliceous materials mentioned herein and phosphoric acid mixturescontaining orthophosphoric acid, pyrophosphoric, triphosphoric, andother polyphosphoric acids.

Another acid of phosphorus which may be employed in the manufacture ofcomposite catalysts according to the present invention istetraphosphoric acid. It has the general formula H6P4013 whichcorresponds to the double oxide formula 3H2O.2P2O5 which in turn may beconsidered as the acid resulting when three molecules of Water are lostby four molecules of orthophosphoric acid H3PO4. The tetraphosphoricacid may be manufactured by the gradual and controlled dehydration byheating of orthophosphoric acid or pyrophosphoric acid or by addingphosphorus pentoxide to these acids in proper amounts. When the latterprocedure is followed, phosphoric anhydride is added gradually until itamounts to 520% by weight of the total water present. After aconsiderable period of standing at ordinary temperature, the crystals ofthe tetraphosphoric acid separate from the viscous liquid and it isfound that these crystals melt at approximately 93 F. and have aspecific gravity of 1.1886 at a temperature of 60 F. However, it isunnecessary to crystallize the tetraphosphoric acid before employing itin the preparation of the solid catalysts inasmuch as the crudetetraphosphoric acid mixture may be incorporated with the alkylorthosilicate.

The alkyl orthosilicates used in the preparation of the catalysts as setforth herein may be regarded as esters of silicic acid and these organicoxygen-containing compounds of silicon have the general formula Si(OR)4in which R represents an alkyl group generally containing from 1 toabout 5 carbon atoms, although these alkyl groups may also sometimescontain more than 5 carbon atoms. The alkyl orthosilicates referred foruse in this process include methylorthosilicate, ethylorthosilicate, andthe propylorthosilicates.

Catalysts may be prepared from an acid of phosphorus, such asorthophosphoric acid, pyrophosphoric acid, triphosphoric acid, ortetraphosphoric acid and an alkyl orthosilicate. These mentionedstarting materials used in this catalyst preparation process are mixedgenerally at a temperature of from about 50 to about 700 F. to form anaggregate in which the phosphoric acid content is usually in majorproportion by weight.

During themixing of a phosphoric acid and an alkyl orthosilicate even ata temperature as low as about 50 R, an alcohol, ROH, or its equivalent,is formed from 3 V V the alkyl orthosilicate-phosphoric acid mixture andan aggregate is formed by removal of the alcohol on further heating. Theaggregate formed from phosphoric acid and these alkyl orthosilicates isa slightly moist to ahnost dry material, which on the addition of water,when necessary, and on being compressed, becomes sufficiently plastic topermit extrusion and cutting operations to produce catalyst particles.These extruded particles are then heated at a temperature of from about200 to about 1000 F. for a time of from about 0.25 to about hours. Thisheating or calcining treatment of the formed particles of catalyst isusually carried out in a substantially inert gas as air, nitrogen, fluegases, and the like.

The resultant catalyst which has been calcined is active forpolymerizing olefinic hydrocarbons particularly for polymerizingnormally gaseous olefinic hydrocarbons to form normally liquidhydrocarbons suitable for use as constituents of gasoline. When employedin the conversion of olefinic hydrocarbons into polymers, the calcinedcatalyst formed as herein set forth, is preferably employed as agranular layer in a heated reactor, which is generally made from steel,and through which the preheated hydrocarbon fraction is directed. Thusthe solid catalyst of this process may be employed for treating mixturesof olefin-containing hydrocarbon vapors to effect olefin polymerization,but this same catalyst may also be used at operating conditions suitablefor maintaining liquid phase operation during polymerization of olefinichydrocarbons, such as butylenes, to produce gasoline fractions. Whenemployed in the polymerization of normally gaseous olefins, the formedand calcined catalyst particles are generally placed in a vertical,cylindrical treating tower and the olefin-containing gas mixture ispassed downwardly therethrough at a temperature of from about 350 toabout 550 F. and at a pressure of 100 to about 1500 pounds per squareinch. These conditions are particularly applicable when dealing witholefin-containing material such as stabilizer reflux which may containfrom approximately 10 to 50% or more of propylene and butylene. Whenoperating on a mixture comprising essentially butanes and butylenes,this catalyst is effective at conditions favoring the maximumutilization of both normal butylenes and isobutylene which involvesmixed polymerization at temperatures of from approximately 250 to about325 F. and at pressures of from about 500 to about 1500 pounds persquare inch.

In utilizing the catalysts of this invention for promoting miscellaneousorganic reactions, the catalysts may be employed in essentially the sameway as they are used when polymerizing olefins in case the reactions areessentially vapor phase and they also may be employed in suspension inliquid phase in various types of equipment.

With suitable modifications in the details of operation, the presenttype of catalyst may be employed in a large number of organic reactionsincluding polymerization of olefins as already mentioned. Typical casesof reactions in which the present type of catalyst may be used are thealkylation of cyclic compounds with olefins, the cyclic compoundsincluding aromatics, polycyclic compounds, naphthenes, and phenols;condensation reactions such as those occurring between ethers andaromatics, alcohols and aromatics, phenols and aldehydes, etc.;reactions involving the hydrohalogenation of unsaturated organiccompounds, isomerization reactions, ester formation by the interactionof earboxylic acids and olefins, and the like. The specific procedurefor utilizing the present type of catalyst in miscellaneous organicreactions will be determined by the chemical and physicalcharacteristics and the phase of the reacting constituents.

During use of these catalysts in vapor phase polymerizations and othervapor phase treatments of organic compounds, it is often advisable toadd small amounts of moisture to prevent excessive dehydration andsubsequent decrease in catalyst activities. In order to substaniiallyprevent loss of water from the catalyst, an amount of water or watervapor such as steam is added to the charged olefin-containing gas so asto substantially balance the vapor pressure of the catalyst. This amountof water vapor varies from about 0.1 to about 6% by volume of theorganic material charged.

Solid phosphoric acid catalysts which have been prepared heretofore bycalcining the composite of a siliceous adsorbent and a phosphoric acidare less active in promoting olefin polymerization reactions than theare catalysts produced by this process. In this process, catalysts ofthese high activities and good crushing strength are formed bycompositing from about 16 to about 79% by weight of a phosphoric acidcalculated on a water-free basis with from about 21 to about 84% byweight of an alkyl orthosilicate. It is generally preferable to reactfrom about 16 to about 63% by weight of phosphoric acid and from about37 to about 84% by weight of an alkyl orthosilicate to produce activecatalyst composites. When the alkyl orthosilicate used is ethylorthosilicate, it is generally advisable to commingle from about 25 toabout 55% by Weight of a phosphoric acid with from about 45 to about 75%by weight of the ethyl orthosilicate to form an aggregate suitable forextrusion and to form catalyst particles. In general, the proportions ofstarting materials are such that the resultant composite of phosphoricacid and silica contains from about 50 to about 75% by weight ofphosphoric acid calculated as P205 and from about 25 to about 50% byweight of silica. Orthophosphoric acid or pyrophosphoric acid and ethylorthosilicate may thus be reacted to give a composite which, afterdrying and calcining, has an unexpected high activity along with goodcrushing strength during use for olefin polymerization reactions,particularly polymerization of propylene and higher olefins.

The following examples of the preparation of catalysts comprised withinthe scope of this invention and the results obtained in their use forcatalyzing the polymerization of propylene are characteristic, althoughthe exact details set forth in these examples are not to be construed asimposing undue limitations upon the generally broad scope of theinvention.

ethyl orthosilicate and orthophosphoric acid: to 107 grams oforthophosphoric acid, containing 85.7% by weight of H3PO4, in an openevaporating dish was added with stirring 116.5 grams of ethylorthosilicate. The mixture became a white jelly-like mass and itstemperature increased to about F. The mixture was then allowed to standfor one hour with an occasional stirring and was then dried under a heatlamp. The evaporation loss was 101.6 grams, which corresponds closely tothe calculated 103 grams loss which would be expected for the evolutionof ethyl alcohol formed from the ethyl orthosilicate. As the resultantwhite powder was too dry for extrusion, it was moistened with 35 cc. ofwater to form a paste-like material which was again subjected to a heatlamp until a moist powder Weighing 134.1 grams was formed into suitablestate for extrusion. This plastic material was extruded twice and formedinto 5 x 5 mm. pellets; these pellets were dried first for one hour at atemperature of 392 F. and then portions were calcined further at 680 and860 F. for one hour each. The pellets which had been calcined at atemperature'of 680 F. had an average bulk density of 0.713 gram per m1.and a crushing strength of 7.9 pounds, While. the pellets similarlycalcined at a temperature of 860 F. for one hour had an average bulkdensity of 0.707 and a crushing strength of 11.1 pounds.

The table shows comparative results obtained in autoclave tests onpolymerization catalysts prepared from crthophosphoric acid and ethylorthosilicate vs. similar tests with samples of a commercially availablepolymerization catalyst. These catalyst activity tests were carried outby placing grams of catalyst pellets (5 x 5 mm.) and 100 grams of apropane-propylene mixture (SO-65% propylene content) in a rotatablesteel autoclave of 850 ml. capacity which was then rotated at atemperature of 450 F. for two hours. At the end of this time,determinations were made to show the percentage conversion of propyleneinto liquid polymers.

Table PROPYLENE POLYMERIZING ACTIVITIES AND CRUSH- IN QT'REN PH OFCATALYSTS PREPARED FROM gltgfilOPHOSPHDRIC ACID AND EIHYL OB'lIIOSlLl-[Test conditions: 10 grams catalyst pellets, 100 grams propane-propylenemixture, maintained for two hours at a temperature of 450 F. in an 850cc. rotating steel autoclave] From the above table, it can be seen thatcatalysts prepared frorn an alkyl orthosilicate, and particularly fromethyl orthosilicate, have an unexpectedly high activity for theconversion of olefins, particularly propylene. The catalysts in theabove table prepared from kieselguhr were samples of a commercialcatalyst sold for the conversion of olefins into higher boilingpolymers. Thus, it is apparent that the catalysts prepared in the mannerof the present invention have unexpectedly higher activities thansimilar silica-containing catalysts, since kieselguhr is essentiallysilica containing very minor amounts of trace impurities such as ironand sodium. While the crushing strengths of the catalysts prepared inaccordance with the example are not as high as those similar crushingstrengths of the samples of commercial polymerization catalysts, it willbe noted that their strengths after use were very similar.. Thus thecatalysts prepared in the manner of the present invention do not sulfera drop in crushing strength over the same period of time, which is assharp in proportion as that experienced with the samples of a commercialpolymerization catalyst.

I claim as my invention:

1. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting a phosphoric acid and an alkylorthosilicate having from 1 to about 5 carbon atoms in each alkyl group,drying and calcining the resultant reaction product.

2. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting a polyphosphoric acid and an alkylorthosilicate having from 1 to about 5 carbon atoms in each alkyl group,drying and calcining the resultant reaction product.

3. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting a polyphosphoric acid and ethylorthosilicate, drying and calcining the resultant reaction product.

4. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 79% by weightof a phosphoric acid, and from about 21 to about 84% by Weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup, drying and calcining the resultant reaction product.

5. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 79% by weightof a phosphoric acid, and from about 21 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at a temperature of from about 50 to about 700 F., drying andcalcining the resultant reaction product.

6. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 79% by weightof a phosphoric acid, and from about 21 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at a temperature of from about 50 to about 700 F., drying, andcalcining the resultant reaction product at a temperature of from about200 to about 1000 F.

7. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 79% by weightof a phosphoric acid, and from about 21 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at a temperature of from about 50 to about 700 F., drying, andcalcining the resultant reaction provided at a temperature of from about200 to about 1000 F. for a time of from about 0.25 to about 10 hours.

8. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 63% by weightof a phosphoric acid, and from about 37 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at atemperature of from about 50 to about 700 F., drying andcalcining the resultant reaction product.

9. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 63% by weightof a phosphoric acid, and from about 37 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at a temperature of from about 50 to about 700 F., drying, andcalcining the resultant reaction product at a temperature of from about200 to about 1000 F.

10. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 16 to about 63% by Weightof a phosphoric acid, and from about 37 to about 84% by weight of analkyl orthosilicate having from 1 to about 5 carbon atoms in each alkylgroup at a temperature of from about 50 to about 700 F., drying, andcalcining the resultant reaction product at a temperature of from about200 to about 1000 F. for a time of from about 0.25 to about 10 hours.

11. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 25 to about 55% by weightof a phosphoric acid, and from about 45 to about by weight of ethylorthosilicate at a temperature of from about 50 to about 700 F., dryingand calcining the resultant reacting prodnot.

12. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 25 to about 55% by weightof a phosphoric acid, and from about 45 to about 75 by weight of ethylorthosilicate at a temperature of from about 50 to about 700 F., drying,and calcining the resultant reaction product at a temperature of fromabout 200 to about 1000 F.

13. A process for manufacturing a highly active solid phosphoric acidcatalyst which comprises reacting from about 25 to about 55% by weightof a phosphoric acid, and from about 45 to about 75% by weight of ethylorthosilicate at a temperature of from about 50 to about 700 F., drying,and calcining the resultant reaction product at a temperature of fromabout 200 to about 1000 F. for a time of from about 0.25 to about 10hours.

References Cited in the file of this patent UNITED STATES PATENTS2,030,048 Brown Feb. 11, 1936 2,317,803 Reeves et a1 Apr. 27, 1943

1. A PROCESS FOR MANUFACTURING A HIGHLY ACTIVE SOLID PHOSPHORIC ACIDCATALYST WHICH COMPRISES REACTING A PHOSPHORIC ACID AND AN ALKYLORTHOSILICATE HAVING FROM 1 TO ABOUT 5 CARBON ATOMS IN EACH ALKYL GROUP,DRYING AND CALCINING THE RESULTANT REACTION PRODUCT.